Invasive primary producers can dramatically reorganize food webs through detrital subsidies. This study assessed (1) contributions of the invasive alga Caulerpa taxifolia to detrital resources of temperate Australian estuaries, and (2) effects of these contributions on sedimentdwelling invertebrates. In an invaded estuary, sampling of an intertidal shore indicated C. taxifolia fragments were consistently present in organic matter deposits and were particularly abundant following storms. Sampling of the alga across 6 invaded estuaries showed that the ratio of organic carbon to nitrogen (C:N) in fresh tissue varied between 7 and 16. To determine how C. taxifolia detritus influences benthic macrofaunal assemblages and whether this influence depends on the quantity and C:N ratio of C. taxifolia detritus, a manipulative field experiment was performed. On a sheltered intertidal mudflat, 0.25 m 2 plots of sediment were experimentally enriched with either a high (90 g DW) or low (30 g) loading of high C:N (14) or low C:N (7) C. taxifolia detritus. Experimental enrichment negatively affected the total abundance and species richness of macroinvertebrates relative to controls, and these effects increased with detrital loading. For some macrofauna, reducing the C:N ratio tended to exacerbate negative effects on abundances, whereas it moderated these effects for other species. Given that organic matter derived from invasive species can be transported beyond the distribution of live invaders, greater consideration should be given to the potential broad-scale effects of invasive primary producers on detrital pathways. KEY WORDS: Detritus · Caulerpa taxifolia · Food quality · Invasion · Nitrogen content · Spatial subsidy Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 420: [73][74][75][76][77][78][79][80][81] 2010 sources, typically degrades rapidly and produces a short-term nutritional source to fast growing consumers (Tenore 1977). Although the C:N ratio of detritus can change during degradation (Anderson 1973, Suberkropp et al. 1976, the starting C:N ratio is a good predictor of decomposition rate (Enriquez et al. 1993).Invasive primary producers are an increasingly large component of detrital pools (Kennedy & Hobbie 2004, Rodil et al. 2008 and have the potential to markedly alter their value. Many successful invaders have rapid individual growth, early maturity, a short life span, high fecundity, minimal structural defence and extensive dispersal capacity (Lodge 1993, Schaffelke et al. 2006. Consequently, invasive primary producers tend to generate large amounts of labile detritus with a low C:N ratio, which is more readily decomposed than is litter from native species (Vitousek et al. 1987, Ashton et al. 2005. Whereas small amounts of refractory detritus may fuel productivity, large quantities of labile detritus may induce sediment anoxia (Pearson & Rosenberg 1978). This phenomenon may be exacerbated in areas of nutrient enrichment where invasive primary producer...

A method for the production of multiple clonal plantlets of Pinuscaribaea var. hondurensis Morlet, P. oocarpa Schiede, and P. tecunumanii Equiluz and Perry (P. patula Schiede and Deppe ssp. tecunumanii (Equiluz and Perry) Styles) from juvenile sources is described. The procedure is based on the spontaneous production of axillary shoots following shoot elongation. Much interclonal variation exists with respect to expiant multiplication. The addition of activated charcoal (0.1%) stimulates shoot elongation, especially in recalcitrant clones of P. caribaea. Axillary bud initiation may be stimulated by 6-benzylaminopurine, but levels above 1 μM can result in failure of induced buds to form shoots. Rooting occurs at about 50% in nonsterile peat–perlite medium without auxin pretreatment. Rooted plantlets can be readily hardened and will grow normally in the glasshouse.

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Manipulations of fully grown (> 60.0 mm) detritivorous Sydney mud whelks Pyrazus ebeninus Brugiere 1972 suggest that the species serves as a 'trophic cul-de-sac', limiting flow of carbon from producers to top consumers. However, although large P. ebeninus individuals experience negligible predation, smaller individuals that do not cause the same depletion of primary and secondary producers may suffer predatory losses. To assess the role that predation on the small whelks might play in weakening the trophic cul-de-sac provided by larger conspecifics, we investigated sizeand habitat-specific patterns of predation on P. ebeninus through a series of field and laboratory experiments. Field tethering of 3 size classes of snail indicated that irrespective of seasonal differences in predation intensity, small (30.1 to 40.0 mm shell height, SH) individuals experienced significantly greater predatory mortality (25% over 7 wk) than medium (50.1 to 60.0 mm SH: 7.5%) or large (70.1 to 80.0 mm SH: 2%) conspecifics. Predatory mortality was largely attributable to naticid predators, although several tethered snails were crushed, perhaps by elasmobranchs, toadfish or crabs. For some size classes there were differences in predatory mortality between low shore mudflats and higher shore mangrove forests, but the direction of these differences varied between autumn and spring, and the differences disappeared altogether when densities of predators were held constant, indicating that they were not driven by habitat per se. In laboratory experiments, the relative contributions of small, medium and large P. ebeninus individuals to the total prey consumed by the naticid gastropod Conuber sordidus Swainson 1821 were similar between choice and no-choice experiments, and even in the absence of small prey items, large P. ebeninus snails were not consumed. Thus, even when there is depletion of small size classes of P. ebeninus, it is unlikely that common benthic predators would consume sufficient numbers of large snails to prevent deleterious effects of this species on primary and secondary production. To the contrary, predatory mortality of small P. ebeninus individuals may ensure that its populations continue to be dominated by the large, damage-causing size classes.KEY WORDS: Detritus-based food web · Naticid · Predation · Pyrazus ebeninus · Trophic cul-de-sac Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 354: [75][76][77][78][79][80][81][82][83] 2008 higher trophic levels (Cebrián 2004), increasing evidence suggests that this is not always the case (Bishop et al. 2007a). Some large detritivorous invertebrates appear to short-circuit trophic transfer by decreasing the abundance of other softer-bodied or smaller invertebrates that are important prey sources for consumers, such as birds and fish, while themselves suffering negligible predation. Recent experiments suggest that the Sydney mud whelk Pyrazus ebeninus Brugiere 1972 may be one such 'trophic cul-de-sac' (Bishop et al. 2...